<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>Document</title>
  <style lang="css">
    button {
      outline: none;
      border: none;
      cursor: pointer;
      color: white;
      position: relative;
      padding: 0.5em 1em;
      background-color: #40a9ff;
    }

    button {
      z-index: 1;
      overflow: hidden;
    }

    button::before {
      z-index: -1;
      content: "";
      position: absolute;
      top: 50%;
      left: 50%;
      width: 1em;
      height: 1em;
      border-radius: 50%;
      background-color: #9254de;
      transform-origin: center;
      transform: translate3d(-50%, -50%, 0) scale(0, 0);
      transition: transform 0.45s ease-in-out;
    }

    button:hover::before {
      transform: translate3d(-50%, -50%, 0) scale(15, 15);
    }
  </style>
</head>

<body>
  <button>兔子零</button>
</body>

</html>